Pre-plant incorporation of compost as a non-fumigant alternative to promote the establishment of fruit trees at old orchard sites

Poor growth of newly planted fruit trees in soil that has previously been used for tree-fruit production presents a significant barrier to the establishment of productive orchards at old orchard sites, and has often been associated with high soil populations of the root-lesion nematode (Pratylenchus penetrans (Cobb) Filipjev and Shuurmans Stekhoven). Recent changes to pesticide regulations now limit access to soil fumigants, increasing interest in alternatives for disease control. Preplant soil incorporation of compost shows potential to suppress P. penetrans in perennial cropping systems. Using a field and greenhouse experiment, this study aimed to evaluate the potential of composts to improve replant establishment of fruit trees in old orchard soil. In the field experiment, preplant incorporation of agricultural waste compost (AWC) combined with surface application of bark chip mulch, as well as mulch alone, resulted in greater trunk diameter increase of sweet cherry trees relative to that of the control and fumigation treatments over the first three years of orchard establishment. AWC, mulch, and AWC+mulch provided sustained nematode control over the first three years. In the greenhouse experiment, compost amendments increased apple seedling shoot weight in 44.4% of the compost type×orchard site combinations evaluated. Similarly, compost amendments resulted in significantly smaller P. penetrans populations relative to that of the control in 22.2% of the compost type × orchard site combinations. Overall, compost shows potential as an alternative to fumigation for control of replant disease; however, future studies should be directed toward understanding the underlying mechanisms behind variation in compost-induced nematode control and plant growth promotion in different orchard soils.